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Fapy•dG (N6-(2-deoxy-α,β-D-erythro-pentofuranosyl)-2,6-diamino-4-hydroxy-5-formamidopyrimidine) and 8-OxodGuo (8-oxo-7,8-dihydro-2′-deoxyguanosine) are major products of 2′-deoxyguanosine oxidation. Fapy•dG is unusual in that it exists as a dynamic mixture of anomers. Much less is known about the effects of Fapy•dG than 8-OxodGuo on transcriptional bypass. The data presented here indicate that T7 RNA polymerase (T7 RNAP) bypass of Fapy•dG is more complex than that of 8-OxodGuo. Primer-dependent transcriptional bypass of Fapy•dG by T7 RNAP is hindered compared to 2′-deoxyguanosine. T7 RNAP incorporates cytidine opposite Fapy•dG in a miniscaffold at least 13-fold more rapidly than A, G, or U. Fitting of reaction data indicates that Fapy•dG anomers are kinetically distinguishable. Extension of a nascent transcript past Fapy•dG is weakly dependent on the nucleotide opposite the lesion. The rate constants describing extension past fast- or slow-reacting base pairs vary less than twofold as a function of the nucleotide opposite the lesion. Promoter-dependent T7 RNAP bypass of Fapy•dG and 8-OxodGuo was carried out side by side. 8-OxodGuo bypass results in >55% A opposite it. When the shuttle vector contains a Fapy•dG:dA base pair, as high as 20% point mutations and 9% single-nucleotide deletions are produced upon Fapy•dG bypass. Error-prone bypass of a Fapy•dG:dC base pair accounts for ∼9% of the transcripts. Transcriptional bypass mutation frequencies of Fapy•dG and 8-OxodGuo measured in RNA products are comparable to or greater than replication errors, suggesting that these lesions could contribute to mutations significantly through transcription. [ABSTRACT FROM AUTHOR]

Organic synthesis provides an accessible route to preparative scale biological glycans, although schemes to access these complex structures are often complicated by preparation of multiple monosaccharide building blocks. Bimodal glycosyl donors capable of forming both α‐ and β‐anomers selectively, are an emerging tactic to reduce the required number of individual synthetic components in glycan construction. This review discusses examples of bimodal donors in the literature, and how they achieve their stereocontrol for both anomers. Notable examples include a bespoke O‐2 benzyl protecting group, a strained glycal for reaction using organometallic catalysis, and a simple perbenzylated donor optimised for stereoselective glycosylation through extensive reaction tuning. [ABSTRACT FROM AUTHOR]

This article highlights the fundamental aspects of hydrophilic interaction liquid chromatography (HILIC) on poly-hydroxyl stationary phases to analyze non-derivatized mono- and disaccharides, including commonly consumed carbohydrates like glucose, fructose, sucrose, and lactose. The evaporative light-scattering detector (ELSD) is utilized as an alternative to an MS detector, and the separation system's selectivity allows the separation of anomers of monosaccharides. The study also includes a rapid method for determining isomaltulose (Palatinose), which was validated and applied to food supplement samples available in the Czech market, even those with high protein content. Additionally, isomaltulose was separated from sucrose in just 13 min. [ABSTRACT FROM AUTHOR]

Simultaneous chromatographic separation of the anomers of saccharides was achieved by using a polymer zwitterionic stationary phase functionalized by acrylamide‐type sulfobetaine. By optimization of separation parameters including column temperature, pH, and flow rate, the column operated in hydrophilic interaction chromatography mode exhibited excellent separation selectivity toward five monosaccharides and their anomers (including ribose, xylose, galactose, glucose, and arabinose) and two disaccharides (lactose and maltose). Baseline separation could be achieved at mild operation conditions such as 20–30°C of column temperature or typical mobile phase composition (85% acetrontrile–15% 20 mM ammonium formate [NH4FA]) with wide pH tolerance range of 2–8. This offers a rapid way to determine the configuration of α or β anomer of the saccharides. [ABSTRACT FROM AUTHOR]

Background: Over the last decades, many strategies to procure and improve xylose consumption in Saccharomyces cerevisiae have been reported. This includes the introduction of efficient xylose-assimilating enzymes, the improvement of xylose transport, or the alteration of the sugar signaling response. However, different strain backgrounds are often used, making it difficult to determine if the findings are transferrable both to other xylose-consuming strains and to other xylose-assimilation pathways. For example, the influence of anomerization rates between α- and β-xylopyranose in pathway optimization and sugar sensing is relatively unexplored. Results: In this study, we tested the effect of expressing a xylose epimerase in S. cerevisiae strains carrying different xylose-consuming routes. First, XIs originating from three different species in isogenic S. cerevisiae strains were tested and the XI from Lachnoclostridium phytofermentans was found to give the best performance. The benefit of increasing the anomerization rate of xylose by adding a xylose epimerase to the XI strains was confirmed, as higher biomass formation and faster xylose consumption were obtained. However, the impact of xylose epimerase was XI-dependent, indicating that anomer preference may differ from enzyme to enzyme. The addition of the xylose epimerase in xylose reductase/xylitol dehydrogenase (XR/XDH)-carrying strains gave no improvement in xylose assimilation, suggesting that the XR from Spathaspora passalidarum had no anomer preference, in contrast to other reported XRs. The reduction in accumulated xylitol that was observed when the xylose epimerase was added may be associated with the upregulation of genes encoding endogenous aldose reductases which could be affected by the anomerization rate. Finally, xylose epimerase addition did not affect the sugar signaling, whereas the type of xylose pathway (XI vs. XR/XDH) did. Conclusions: Although xylose anomer specificity is often overlooked, the addition of xylose epimerase should be considered as a key engineering step, especially when using the best-performing XI enzyme from L. phytofermentans. Additional research into the binding mechanism of xylose is needed to elucidate the enzyme-specific effect and decrease in xylitol accumulation. Finally, the differences in sugar signaling responses between XI and XR/XDH strains indicate that either the redox balance or the growth rate impacts the SNF1/Mig1p sensing pathway. [ABSTRACT FROM AUTHOR]

The fragmentation mechanism of D‐glucose was investigated in detail by two different fragmentation techniques, namely, collision‐induced dissociation (CID) and infrared multiphoton dissociation (IRMPD) using all six 13C‐labeled isotopomers and 2H‐labeled isotopomers. For both CID and IRMPD energy‐resolved measurements were carried out. Individual fragmentation pathways were studied at MS2 and MS3 levels. Additionally, we have developed an HPLC‐tandem MS method to separate the anomers of D‐glucose using a HILIC column and investigated their fragmentation patterns individually. We propose a complete fragmentation landscape of D‐glucose, demonstrating that a rather simple multifunctional molecule displays extreme complexity in gas phase dissociation, following multiple parallel fragmentation routes yielding a total of 23 distinct fragment ions. The results allowed a detailed formulation of the complex fragmentation mechanism of D‐glucose. The results have immediate consequences for the full structure analysis of complex carbohydrates. [ABSTRACT FROM AUTHOR]

The synthesis and antiribosomal and antibacterial activity of both anomers of a novel apralog, 5-O-(5-amino-3-C-dimethylaminopropyl-D-ribofuranosyl)apramycin, are reported. Both anomers show excellent activity for the inhibition of bacterial ribosomes and that of MRSA and various wild-type Gram negative pathogens. The new compounds retain activity in the presence of the aminoglycoside phosphoryltransferase aminoglycoside modifying enzymes that act on the primary hydroxy group of typical 4,5-(2-deoxystreptamine)-type aminoglycoside and related apramycin derivatives. Unexpectedly, the two anomers have comparable activity both for the inhibition of bacterial ribosomes and of the various bacterial strains tested. [ABSTRACT FROM AUTHOR]

Minimally protected aminopolyols are novel substrates for the galactose oxidase variant F2. Site-selective oxidation proceeds at the terminal primary alcohol, followed by spontaneous cyclisation to afford stable hemiaminal/hemiacetal anomers of the piperidine and azepane scaffolds, with isolated yields of up to 94%. Simultaneous deprotection and reduction occured readily to afford valuable and biologically relevant iminosugars. [ABSTRACT FROM AUTHOR]

In High-Performance Liquid Chromatography (HPLC), the separation of reducing sugars can typically show three possible typologies of chromatographic profiles (i.e., single peak, two resolved peaks and two peaks interconnected by a plateau) due to the rate at which the relevant α/β anomers interconversion (anomerization) can take place in relation to their elution-time. By analyzing these chromatographic profiles, thermodynamic and kinetic properties of anomerization phenomenon can be extrapolated. In this work we studied the anomerization of some monosaccharides by using a recently developed photo-click cysteine-based stationary phase through dynamic hydrophilic interaction liquid chromatography (D-HILIC) conditions. In the 5–25 °C temperature range, the ΔG#α→β and ΔG#β→α barriers were found to achieve values within the interval 21.1/22.2 kcal/mol for glucose, with differences between α→β and β→α reactions of about 0.4 kcal/mol. For xylose, in the same temperature range, the ΔG#α→β and ΔG#β→α barriers are between 20.7 to 21.5 kcal/mol, with differences between α→β and β→α reactions of about 0.2 kcal/mol. The experimental data are in agreement with those reported in literature, confirming the this new stationary phase using HILIC conditions is a robust platform to measure kinetic and thermodynamic properties of the isomerization reaction. [ABSTRACT FROM AUTHOR]

Simple Summary: All livings are composed of cells, which contain lipid, proteins, nuclei acids, and saccharides. Saccharides include polysaccharides, oligo saccharides, disaccharides, which are linked by monosaccharides. Monosaccharides such as glucose exist in two forms, named α and β anomer, in solution. In addition, monosaccharides could be linked with lipid, proteins, nuclei acids or other saccharide to form glycosides through glycosylation. In nature, glycosylation is catalyzed by enzymes. Until now, all enzymes catalyzed glycosylation to form glycosides with either α or β form but not both. This study found an enzyme, amylosucrase from Deinococcus geothermalis (DgAS), could catalyze glycosylation of a kind of lipid named ganoderic acids triterpenoids from a medicinal fungus Ganoderma lucidum to form both α and β anomer of glycosides. This is the first report that enzymes could catalyze such glycosylation and a possible reaction mechanism was proposed. Glycosylation occurring at either lipids, proteins, or sugars plays important roles in many biological systems. In nature, enzymatic glycosylation is the formation of a glycosidic bond between the anomeric carbon of the donor sugar and the functional group of the sugar acceptor. This study found novel glycoside anomers without an anomeric carbon linkage of the sugar donor. A glycoside hydrolase (GH) enzyme, amylosucrase from Deinococcus geothermalis (DgAS), was evaluated to glycosylate ganoderic acid F (GAF), a lanostane triterpenoid from medicinal fungus Ganoderma lucidum, at different pH levels. The results showed that GAF was glycosylated by DgAS at acidic conditions pH 5 and pH 6, whereas the activity dramatically decreased to be undetectable at pH 7 or pH 8. The biotransformation product was purified by preparative high-performance liquid chromatography and identified as unusual α-glucosyl-(2→26)-GAF and β-glucosyl-(2→26)-GAF anomers by mass and nucleic magnetic resonance (NMR) spectroscopy. We further used DgAS to catalyze another six triterpenoids. Under the acidic conditions, two of six compounds, ganoderic acid A (GAA) and ganoderic acid G (GAG), could be converted to α–glucosyl-(2→26)-GAA and β–glucosyl-(2→26)-GAA anomers and α-glucosyl-(2→26)-GAG and β-glucosyl-(2→26)-GAG anomers, respectively. The glycosylation of triterpenoid aglycones was first confirmed to be converted via a GH enzyme, DgAS. The novel enzymatic glycosylation-formed glycoside anomers opens a new bioreaction in the pharmaceutical industry and in the biotechnology sector. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) is an established treatment modality for a range of superficial and localized cancers. There has been tremendous interest in the development of advanced photosensitizers that exhibit superior photophysical properties, high tumor selectivity, and improved pharmacokinetics. Glucose is one of the well-studied targeting moieties that can deliver various therapeutic agents to cancer cells selectively via the Warburg effect. However, the use of glucosylated photosensitizers for targeted PDT has remained little studied and to the best of our knowledge, the PDT effect of the positional isomers of these conjugates has never been compared. We report herein the preparation and photophysical properties of the C1α and C1β anomers of a glucosylated boron dipyrromethene-based photosensitizer. The cellular uptake and photocytotoxicity of both anomers were also studied and compared using A549 human lung carcinoma cells and HEK293 human embryonic kidney cells. Interestingly, the cellular uptake of the C1α anomer was approximately 2-fold higher than that of the C1β anomer regardless of the cell type and incubation time. The uptake pathway of both anomers was also studied. It was found that they were internalized through energy-dependent receptor/protein-mediated endocytosis rather than the well-known glucose transporters and sodium-driven glucose symporters. [ABSTRACT FROM AUTHOR]

The importance of knowing the phenomenon of moisture sorption and the microstructural evolution in lactose anomers, lies in being able to establish its applicability. Thus, the moisture sorption phenomenon of four types of lactose anomers (C-βL, S-βL, F-αL and C-αL∙H 2 O) was studied, constructing adsorption isotherms at three storage temperatures (15, 25 and 35 °C), and fitting the experimental data with four mathematical models (BET, GAB, Peleg and Caurie). The analysis of the adsorption isotherm data, showed that: (i) β-lactose anomers adsorb less moisture than α-lactose anomers. (ii) In β-lactose anomers, purity influences stability, keeping a broad range of water activities. (iii) Increasing the storage temperature reduces the water activity range in which the anomers are stable. (iv) Based on the R2 parameter at 15 °C the best fit was achieved by employing the GAB model for the four lactose isomers, Specifically, the R2 values were as follows: C-βL = 0.993, S-βL = 0.996, F-αL = 0.905, and C-αL∙H 2 O = 0.98. The morphological evolution of lactose particles studied by scanning electron microscopy (SEM) showed particles of irregular morphology in the α-lactose anomers. Commercial β-lactose anomer presented particles with irregular morphology and few with curved morphology, suggesting the presence α-lactose as contamination. The synthesized β-lactose anomer presented mostly curved particles, indicating its high purity. In β-lactose anomers, mutarotation into α-lactose was observed with increasing storage temperature. • During storage βL presents greater stability (a w = 0.7) than αL∙H 2 O. (a w = 0.5). • Commercial βL contains impurities that cause instability compared to a pure system. • SEM analysis allows characterizing the crystalline structures of βL and αL∙H 2 O. • Temperature and relative humidity promote mutarotation of βL to αL∙H 2 O. [ABSTRACT FROM AUTHOR]

Electroconversion (also known as electroreforming) of biomass-derived compounds is currently attracting considerable interest, with the aim of lowering cell voltage during electrolysis to co-produce a number of decarbonized energy carriers or chemical intermediates (hydrogen, ammonia, gluconate, etc.). Naturally, d -glucose, which represents a study model for the electro-valorization of cellulosic biomass into value-added chemicals such as gluconate, is in fact a mixture of two anomers called α- d - and β- d -glucose. The β- d -glucose anomer is the monomer unit of cellulose, while the α- d -glucose anomer is the monomer unit of starch. In this contribution, we therefore investigate whether or not the nature of the glucose substrate can influence electrolysis cell performance, or whether the use of d -glucose alone can represent the true picture of biomass feeding an electrolysis cell. Free-standing electrocatalysts ready for use in a membrane-electrode assembly were synthesized using a pulsed electrodeposition methodology to control the deposition of gold and platinum particles on the microfibers of a low-metal gas diffusion electrode (GDE). We developed GDE-Au (82 μg Au cm−2, 0.88 wt%) to catalyze the selective electrooxidation of glucose into gluconate, and GDE-Pt (33 μg Pt cm−2, 0.36 wt%) to catalyze the hydrogen evolution reaction (HER). While half-cell studies showed no significant difference, for the glucose-fed electrolysis cell, α- d -glucose leads to a much higher current density compared to d -glucose and β- d -glucose for cell voltages above 0.5 V, leading to 85.6 ± 17.1, 44.3 ± 8.8 and 30.5 ± 0.8 mA cm‒2 for α- d -glucose, β- d -glucose, and d -glucose, respectively, at 1 V. [Display omitted] [ABSTRACT FROM AUTHOR]

Phase transfer catalysis (PTC) is widely used for the preparation of anomerically pure aryl glycosides by glycosylation of phenols with glycosyl halides. Here, we attempted to synthesize 4‐(3‐chloropropoxy)phenyl (CPP) sialoside – a useful Janus glycoside for neoglycoconjugate synthesis. A batch glycosylation reaction under typical PTC conditions (N‐acetylsialyl chloride, 4‐(3‐chloropropoxy)phenol, Bu4NHSO4, AcOEt, 10 % aq Na2CO3) resulted in formation of CPP sialoside as a single anomer, albeit in low yield. Conversely, the PTC glycosylation in flow using Comet X‐01 micromixer doubled the yield of CPP sialoside, which was obtained as a mixture of anomers suggesting the change in the reaction mechanism apparently induced by the change in mixing mode. An increase in flow rate led to further loss of stereoselectivity while the use of T‐shaped mixer increased stereoselectivity. Similar results were obtained for N,N‐diacetylsialyl chloride and two other para‐alkoxy‐substituted phenols suggesting generality of the discovered phenomenon. [ABSTRACT FROM AUTHOR]

Reducing chain ends in various hydrolyzed cellulose samples were quantitatively analyzed by solid-state 13C NMR. Cellulose di- and tetramers served as model systems to demonstrate that distinct signals at 97 ppm and 92.7 ppm can be detected quantitatively and assigned unambiguously to reducing chain ends in β and α anomers, respectively. In standard Avicel microcrystalline cellulose, the same signals were detected at the expected low intensity; their strength increased significantly upon further hydrolysis. The assignment of the 97 and 92.7 ppm signals to reducing chain ends was confirmed by their absence after ethanolysis, which instead produced an α-ethyl-ether end group signal at 99 ppm. Due to moderate-amplitude chain-end mobility, chain-end signals were relatively enhanced in direct-polarization 13C NMR with heteronuclear Overhauser enhancement. In 13C-enriched hydrolyzed cellulose, the assignment of the C–OH chain-end signals was further corroborated by hydroxyl-proton selection and two-dimensional 13C-13C NMR. From the fractional chain-end signal intensity, the number-average degree of polymerization (DPn) was determined. For Avicel, this yielded DPn = 43 (+ 50, -6), consistent with gel-permeation chromatography but significantly lower than deduced from a more indirect optical method likely hampered by limited chain-end accessibility. After 60 min of hydrolysis of ball-milled Avicel or cellulose from maize, highly reliable values of DPn = 18 ± 3 and 15 ± 3, respectively, were obtained. Solid-state NMR completely avoids the potential loss of low-molar-mass chains in solution-based approaches. The accurate, solvent-free solid-state NMR method introduced here can serve as a primary standard to calibrate other methods for molar-mass determination in hydrolyzed cellulose. [ABSTRACT FROM AUTHOR]

Anomeric base pairs in heterochiral DNA with strands in the α‐d and β‐d configurations and homochiral DNA with both strands in α‐d configuration were functionalized. The α‐d anomers of 2′‐deoxyuridine and 7‐deaza‐2′‐deoxyadenosine were synthesized and functionalized with clickable octadiynyl side chains. Nucleosides were protected and converted to phosphoramidites. Solid‐phase synthesis furnished 12‐mer oligonucleotides, which were hybridized. Pyrene click adducts display fluorescence, a few of them with excimer emission. Tm values and thermodynamic data revealed the following order of duplex stability α/α‐d≫β/β‐d≥α/β‐d. CD spectra disclosed that conformational changes occur during hybridization. Functionalized DNAs were modeled and energy minimized. Clickable side chains and bulky click adducts are well accommodated in the grooves of anomeric DNA. The investigation shows for the first time that anomeric DNAs can be functionalized in the same way as canonical DNA for potential applications in nucleic acid chemistry, chemical biology, and DNA material science. [ABSTRACT FROM AUTHOR]

Dodecamer duplex DNA containing anomeric (α/β‐d) and enantiomeric (β‐l/β‐d) 2'‐deoxycytidine mismatches was studied with respect to base pair stability in the absence and presence of silver ions. Stable duplexes with silver‐mediated cytosine–cytosine pairs were formed by all anomeric and enantiomeric combinations. Stability changes were observed depending on the composition of the mismatches. Most strikingly, the new silver‐mediated base pair of anomeric α‐d‐dC with enantiomeric β‐l‐dC is superior to the well‐noted β‐d/β‐d‐dC pair in terms of stability. CD spectra were used to follow global helical changes of DNA structure. [ABSTRACT FROM AUTHOR]

A facile and stereoselective synthesis of Harvestmen lactone 1 was accomplished in a linear synthetic approach over 14 steps with an overall yield of 10.1 %. This total synthesis was carried out using a chiral pool approach from commercially available D‐glucose. The key reactions employed in this synthetic approach were Wittig reaction, Barton‐McCombie Deoxygenation and 2,2,6,6‐Tetramethylpiperidin‐1‐yl)oxyl (TEMPO) mediated radical oxidation. [ABSTRACT FROM AUTHOR]

The β-anomeric form of nicotinamide riboside (NR+) is a precursor for nicotinamide adenine dinucleotide (NAD+), a redox cofactor playing a critical role in cell metabolism. Recently, it has been demonstrated that its chloride salt (NR+Cl−) has beneficial effects, and now NR+Cl− is available as a dietary supplement. Syntheses and studies of analogues and derivatives of NR+ are of high importance to unravel the role of NR+ in biochemical processes in living cells and to elaborate the next generation of NR+ derivatives and conjugates with the view of developing novel drug and food supplement candidates. This review provides an overview of the synthetic approaches, the chemical properties, and the structural and functional modifications which have been undertaken on the nicotinoyl riboside scaffold.

The aim of this study was to develop a novel software platform for the simulation of magnetic resonance spin systems, capable of simulating a large number of spatial points (1283) for large in vivo spin systems (up to seven coupled spins) in a time frame of the order of a few minutes. The quantum mechanical density‐matrix formalism is applied, a coherence pathway filter is utilized for handling unwanted coherence pathways, and the 1D projection method, which provides a substantial reduction in computation time for a large number of spatial points, is extended to include sequences of an arbitrary number of RF pulses. The novel software package, written in MATLAB, computes a basis set of 23 different metabolites (including the two anomers of glucose, seven coupled spins) with 1283 spatial points in 26 min for a three‐pulse experiment on a personal desktop computer. The simulated spectra are experimentally verified with data from both phantom and in vivo MEGA‐sLASER experiments. Recommendations are provided regarding the various assumptions made when computing a basis set for in vivo MRS with respect to the number of spatial points simulated and the consideration of relaxation. [ABSTRACT FROM AUTHOR]

Type IV galactosemia is a recently discovered inherited metabolic disease. It is caused by mutations in the GALM gene which result in reduced activity of the enzyme galactose mutarotase. This enzyme catalyses the interconversion of the α- and β-anomers of d -galactose and some other monosaccharides. Human galactose mutarotase is monomeric and its structure is largely composed of β-sheets. The catalytic mechanism requires a histidine residue acting as an acid, and a glutamate acting as a base. Together, these residues open the pyranose ring of d -galactose enabling free rotation of the bond between the first two carbon atoms in the monosaccharide. This can cause reversal of the configuration of the hydroxyl group attached to carbon 1. Type IV galactosemia manifests with similar symptoms to type II galactosemia (galactokinase deficiency), i.e. early onset cataracts. However, as a recently discovered disease, the longer-term consequences are unknown. The physiological role, if any, of galactose mutarotase's reactions with other monosaccharides are not yet known. The possible associations with other proteins also require further investigation. [ABSTRACT FROM AUTHOR]

Fucosylation of glycans impacts a myriad of physiological and pathological processes. Inhibition of fucose expression emerges as a potential therapeutic avenue for example in cancer, inflammation, and infection. In this study, we found that protected 2‐fluorofucose 1‐phosphate efficiently inhibits cellular fucosylation with a four to seven times higher potency than known inhibitor 2FF, independently of the anomeric stereochemistry. Nucleotide sugar analysis revealed that both the α‐ and β‐GDP‐2FF anomers are formed inside the cell. In conclusion, we developed A2FF1P and B2FF1P as potent new tools for studying the role of fucosylation in health and disease and they are potential therapeutic candidates. [ABSTRACT FROM AUTHOR]

The 13C NMR chemical shifts of some common pyranose monosaccharides in D2O solution were predicted using a combined molecular mechanics (Pcmod 9.1/MMFF94) and ab initio (GIAO (B3LYP/DFT, 6-31G(d))) model. This method has been successfully used for a range of organic molecules in CDCl3 solution but has not previously been used for aqueous solutions. The method gave such good agreement with experiment that the populations of the conformers at C6 of the monosaccharides could be obtained. This has been attempted previously by various methods with diverse results. In all the compounds studied the α and β anomers have similar populations. In glucose the populations of the GG and GT conformers are ca equal with TG a minor component, in galactose GT has the largest population and GG the smallest, in mannose GG is preferred with TG a minor component and in talose GT and TG are favoured with GG a minor constituent. The results are in general agreement with previous work. To our knowledge this is the first time that 13C shifts have been used to determine sugar conformations in solution. The conformation of sucrose in D2O solution was examined by both 1H and 13C NMR. The complete analysis of the 1H NMR spectrum has been achieved and provides information on the preferred conformations of the CH2OH fragments at G6 (GG) and F6 (GG, GT). Calculations of the 13C shifts confirm these results and show also that the conformation at F1 is mainly GG plus TG. The sucrose conformational profile in solution includes the crystal structure together with the above conformations at F1 and F6. [ABSTRACT FROM AUTHOR]

A process for the de novo synthesis of imino‐C‐glycosides is described. The methodology is based on the reaction of 1‐C‐stannylated iminosugars with various electrophiles under the conditions of Migita‐Kosugi‐Stille cross‐couplings, which gives 1‐C‐substituted iminosugar derivatives in a stereoretentive process. The required iminoglycosyl stannanes are obtained by way of the highly stereoselective addition of tributylstannyllithium to (SR)‐ or (SS)‐N‐tert‐butanesulfinyl glycosylamines, followed by an activation cyclization sequence. Most interestingly, the methodology is tunable: the configuration of the tin adduct is controlled exclusively by the tert‐butanesulfinyl auxiliary, thus giving access after ring formation to 'α'‐configured or 'β'‐configured iminoglycosyl stannanes. With the subsequent stereoretentive C−C bond‐forming process, the methodology allows the synthesis of pseudo anomers of imino‐C‐glycosyl compounds in a controlled fashion. [ABSTRACT FROM AUTHOR]

Lactose, the characteristic carbohydrate of milk, is a high-value product applied as an excipient in pharmaceutical formulations and as a carrier in dry-powder inhalers when purified. Usually, lactose is in the mutarotation equilibrium of two anomers in solution, the α and the β forms. This work has dealt theoretically with the mutarotation mechanisms of α-lactose catalyzed by solvent water molecules and acid molecules, including acetic acid (HAc) and trifluoroacetic acid (TFA). The whole mutarotation process is comprised of three stages, i.e., the initial ring-opening step, the isomerization of anomeric carbon C1 followed by the ring-closing step, in which, the ring-opening step involves the highest activation energy and therefore is the rate-determining step. The activation energies along the optimum mutarotation routes catalyzed by H2O, HAc and TFA molecules are 22.1, 13.5 and 8.7 kcal mol−1, respectively. All the transition states involved in the optimum ring-opening/closing reaction coordinates are octatomic ring structures with the presence of two solvent water molecules or one acid molecule. For the acid-catalyzed rate-determining step, the reaction driving force originates from the protonation of the sugar ring O5 atom by the carboxyl hydrogen atom, whereas for the solvent-catalyzed process, it originates from the transfer of C1–hydroxyl hydrogen. The ease of lactose mutarotation depends greatly on the acidity of the catalyst. The obtained observation can provide more valuable information for pharmaceutical science. [ABSTRACT FROM AUTHOR]

The configuration‐dependent self‐association mode of the two anomers of O‐Ac,N‐Fmoc‐d‐glucosamine, a foldamer building block, leading to gel and/or single crystal formation is described. The β‐anomer of the sugar amino acid (2) forms a gel from various solvents (confirmed by SEM, rheology measurements, NMR, and ECD spectroscopy), whereas the α‐anomer (1) does not form a gel with any solvent tested. Transition from the solution state to a gel is coupled to a concurrent shift of the Fmoc‐groups: from a freely rotating (almost symmetrical) to a specific, asymmetric orientation. Whereas the crystal structure of the α‐anomer is built as an evenly packed 3D system, the β‐anomer forms a looser superstructure of well‐packed 2D layers. Modeling indicates that in the lowest energy, but scarcely sampled conformer of the β‐anomer, the Fmoc‐group bends above the sugar moiety, stabilized by intramolecular CH↔π interactions between the aromatic rings. It is concluded that possessing an extended and promiscuous interaction surface and a conformationally heterogeneous solution state are among the basic requirements of gel formation for a candidate molecule. [ABSTRACT FROM AUTHOR]

Five 19F-substituted glucose analogues were used to probe the activity and mechanism of the enzyme mutarotase by using magnetisation-exchange NMR spectroscopy. The sugars (2-fluoro-2-deoxy-d-glucose, FDG2; 3-fluoro-3-deoxy-d-glucose, FDG3; 4-fluoro-4-deoxy-d-glucose, FDG4; 2,3-difluoro-2,3-dideoxy-d-glucose, FDG23; and 2,2,3,3-tetrafluoro-2,3-dideoxy-d-glucose (2,3-dideoxy-2,2,3,3-tetrafluoro-d- erythro -hexopyranose), FDG2233) showed separate 19F NMR spectroscopic resonances from their respective α- and β-anomers, thus allowing two-dimensional exchange spectroscopy measurements of the anomeric interconversion at equilibrium, on the time scale of a few seconds. Mutarotase catalysed the rapid exchange between the anomers of FDG4, but not the other four sugars. This finding, combined with previous work identifying the mechanism of the anomerisation by mutarotase, suggests that the rotation around the C1–C2 bond of the pyranose ring is the rate-limiting reaction step. In addition to d-glucose itself, it was shown that all other fluorinated sugars inhibited the FDG4 anomerisation, with the tetrafluorinated FDG2233 being the most potent inhibitor. Inhibition of mutarotase by F-sugars paves the way for the development of novel fluorinated compounds that are able to affect the activity of this enzyme in vitro and in vivo. Two-dimensional exchange NMR spectroscopy detected rapid anomerisation of 4-fluoro-4-deoxy-d-glucose in the presence of the enzyme mutarotase. We measured the exchange rate constants and inhibition of this reaction by d-glucose and other fluorinated analogues. Implications for studies of the in situ kinetics of these glucose analogues in cells and tissues are discussed. [ABSTRACT FROM AUTHOR]

To synthesize a water-soluble paclitaxel derivative, the anomers of diols of allyl 2,3,4-tri-O-benzyl-6-O-tritylglycoside (maltoside) were prepared, which can be separated by chromatographic procedure. One anomer was converted into α-glycosyloxyacetic acid (maltosyloxyacetic acid) by oxidative cleavage of the diol and subsequent oxidation. Ester-linked paclitaxel-glycoside conjugate, 7- glycolylpaclitaxel 2′′-O-α-maltoside, was provided by condensation of 2′ -TES paclitaxel with α-glycosyloxyacetic acid (maltosyloxyacetic acid) followed by deprotection of hydroxy groups. [ABSTRACT FROM AUTHOR]

The analysis of carbohydrates, or glycans, is challenging for established structure-sensitive gas-phase methods. The multitude of possible stereo-, regio-, and structural isomers makes them substantially more complex to analyze than DNA or proteins, and no one method is currently able to fully resolve them. While the combination of tandem mass spectrometry (MS) and ion-mobility spectrometry (IMS) have made important inroads in glycan analysis, in many cases, this approach is still not able to identify the precise isomeric form. To advance the techniques available for glycan analysis, we employ two important innovations. First, we perform ultrahigh-resolution mobility separation using structures for lossless ion manipulations (SLIM) for isomer separation and pre-selection. We then complement this IMS-MS stage with a cryogenic IR spectroscopic dimension since a glycan's vibrational spectrum provides a fingerprint that is extremely sensitive to the precise isomeric form. Using this unique approach in conjunction with oxygen-18 isotopic labeling, we show on a range of disaccharides how the two α and β anomers that every reducing glycan adopts in solution can be readily separated by mobility and identified based on their IR spectra. In addition to highlighting the power of our technique to detect minute differences in the structure of isomeric carbohydrates, these results provide the means to determine if and when anomericity is retained during collision-induced dissociation (CID) of larger glycans. [ABSTRACT FROM AUTHOR]

Fifteen phenylpropanoid glycosides, including six undescribed compounds were isolated from the fruit of Lycium barbarum L. (Solanaceae) (goji or wolfberry). Their structures were identified by detailed spectroscopic analyses. Seven known compounds were firstly isolated from the genus Lycium , in which the 1D and 2D NMR data of one compound were reported for the first time. Notably, two undescribed compounds were a pair of rare tautomeric glycoside anomers characterized by the presence of free anomeric hydroxy. Antioxidant and hypoglycemic activities of all these compounds were assessed using DPPH radical scavenging, oxygen radical absorbance capacity (ORAC), and α -glucosidase inhibitory assays, respectively. These compounds showed different levels of oxygen radical absorbance capacity, and some isolates exhibited potent antioxidant activity with greater ORAC values than the positive control (EGCG). Image 1 • 15 phenylpropanoid glycosides (six undescribed compounds) were isolated from goji. • Seven known compounds were isolated from the genus Lycium for the first time. • The 1D and 2D NMR data of one known compound were firstly reported. • Two unusual glycosides are characterized by the presence of free anomeric hydroxy. • Some compounds exhibited the greater ORAC values than the positive control (EGCG). [ABSTRACT FROM AUTHOR]

There is increasing biopharmaceutical interest in oligosaccharides and glycosylation. A key requirement for these sample types is the ability to characterize the chain length, branching, type of monomers, and importantly stereochemistry and anomeric configuration. Herein, we showcase the multi-function capability of a cyclic ion mobility (cIM) separator embedded in a quadrupole/time-of-flight mass spectrometer (Q-ToF MS). The instrument design enables selective activation of mobility-separated precursors followed by cIM separation of product ions, an approach analogous to MSn. Using high cIM resolution, we demonstrate the separation of three isomeric pentasaccharides and, moreover, that three components are present for each compound. We show that structural differences between product ions reflect the precursor differences in some cases but not others. These findings are corroborated by a heavy oxygen labelling approach. Using this methodology, the identity of fragment ions may be assigned. This enables us to postulate that the two main components observed for each pentasaccharide are anomeric forms. The remaining low abundance component is assigned as an open-ring form. [ABSTRACT FROM AUTHOR]

Some biogenic substances undergo steric isomerism or tautomerism in which the isomers are unresolvable. Naturally, the isomers are expected to form molecular complexes with distinct stabilities. This paper proposes the method of determining individually the stability constants of complexes formed under isomerisation and complexation equilibria: the NMR titration curves are modelled and formulated for fast and slow isomeric equilibria, the process of least-squares fittings is explained, and the application to supramolecular complexation of unresolvable isomers is discussed as compared with NMR titration data reported for α- and β-D-glucosamine anomers. [ABSTRACT FROM AUTHOR]

The plant Psychotria kirkii hosts an obligatory bacterial symbiont, Candidatus Burkholderia kirkii, in nodules on their leaves. Recently, a glucosylated derivative of (+)‐streptol, (+)‐streptol glucoside, was isolated from the nodulated leaves and was found to possess a plant growth inhibitory activity. To establish a structure–activity relationship study, a convergent strategy was developed to obtain several pseudosugars from a single synthetic precursor. Furthermore, the glucosylation of streptol was investigated in detail and conditions affording specifically the α or β glucosidic anomer were identified. Although (+)‐streptol was the most active compound, its concentration in P. kirkii plant leaves extract was approximately ten‐fold lower than that of (+)‐streptol glucoside. These results provide compelling evidence that the glucosylation of (+)‐streptol protects the plant host against the growth inhibitory effect of the compound, which might constitute a molecular cornerstone for this successful plant‐bacteria symbiosis. Protective glucosylation: A convergent synthetic route was developed to obtain the novel growth plant inhibitor, streptol glucoside, recently isolated from P. kirkii plant leaves extract. The biological activity investigation of the natural product and its derivatives suggests that the glucose of streptol glucoside protects the plant against the potent growth inhibitor streptol. [ABSTRACT FROM AUTHOR]

Abstract Lactose, a disaccharide is a ubiquitous excipient in many pharmaceutical formulations which exists in two anomeric forms; either as α- or β-lactose. The anomers have different properties which can affect their application. Nevertheless, batches of lactose products are widely produced by many manufacturers, and is available in many grades. However, the anomeric content of these batches has not been accurately characterized and reported previously. Therefore, the aim of this study was to analyse a set of 19 commercially available samples of lactose using a novel H1-NMR technique to establish a library showing the anomeric content of a large range of lactose products. The lactose samples were also analysed by DSC. The anomeric content of the α-lactose monohydrate samples were found to vary by more than 10%, which might influence bioavailability from final formulations. The data showed that there is a need to determine and monitor the anomeric content of lactose and this should be a priority to both the manufacturers and the formulators of medicines. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We present a model-based tool for quantitative of benchtop and high field NMR. • The method uses a quantum mechanical model to include higher order coupling. • The approach is field-invariant so is beneficial for analysing benchtop NMR data. • Concentrations of the major sugars were measured with accuracy of <2%. • Low field quantification is insensitive to shift variations. Abstract Recently developed benchtop instruments have the potential of bringing the benefits of NMR spectroscopy to the wide variety of industrial applications. Unfortunately, their low spectral resolution poses significant challenges for traditional quantification approach. Here we present a novel model-based method designed to overcome these challenges. By defining our models in terms of quantum mechanical properties of the underlying spin system, we make our approach invariant to the spectrometer field strength and especially suitable for analyzing benchtop data. Our experimental results on prepared samples and natural fruit juices confirm the applicability of our method for quantitative analysis of medium-field 1 H NMR spectra. The developed method succeeds in accurately separating the spectra of glucose anomers and even monitoring their interconversion in non-deuterated water. Furthermore, the compositions of unbuffered natural fruit juices estimated using data from 43 MHz to 400 MHz spectrometers are in good agreement with each other and with the reference values from nutrition databases. [ABSTRACT FROM AUTHOR]

An efficient synthesis of single a and ß anomers of methyl 2-azido-2-deoxyribofuranoside was accomplished from methyl D-arabinofuranoside via high yielding one-step protection of 3- and 5-hydroxyl groups with the Markiewicz-Wiewiorowski silyl protection, 2-O-triflation, followed by SN2-type displacement of 2-O-triflate with azide and deprotection. The efficient four step protocol required a single column chromatography step. In addition, similar steps were followed for the synthesis of methyl 2-chloro-2- deoxyribofuranoside. [ABSTRACT FROM AUTHOR]

The microalgae Chlorella saccharophila UTEX247 was co-cultured with its symbiotic indigenous isolated bacterial strain, Exiguobacterium sp., to determine the possible effects of bacteria on microalgae growth and lutein productivity. Under optimal conditions, the lutein productivity of co-culture was 298.97 µg L−1 d−1, which was nearly 1.45-fold higher compared to monocultures i.e., 103.3 µg L−1 d−1. The highest lutein productivities were obtained in co-cultures, accompanied by a significant increase in cell biomass up to 0.84-fold. These conditions were analyzed using an untargeted metabolomics approach to identify metabolites enhancing valuable renewables, i.e., lutein, without compromising growth. Our qualitative metabolomic analysis identified nearly 30 (microalgae alone), 41 (bacteria alone), and 75 (co-cultures) metabolites, respectively. Among these, 46 metabolites were unique in the co-culture alone. The co-culture interactions significantly altered the role of metabolites such as thiamine precursors, reactive sugar anomers like furanose and branched-chain amino acids (BCAA). Nevertheless, the central metabolism cycle upregulation depicted increased availability of carbon skeletons, leading to increased cell biomass and pigments. In conclusion, the co-cultures induce the production of relevant metabolites which regulate growth and lutein simultaneously in C. saccharophila UTEX247, which paves the way for a new perspective in microalgal biorefineries. • A new bacteria strain, Exiguobacterium sp., was characterised. • Co-culture conditions were optimized to improve lutein production without compromising growth. • Co-cultures simulated a metabolites-rich phycosphere environment. • Alternations in central carbon metabolism pathways in microalgae were observed due to dynamic metabolic crosstalk. [ABSTRACT FROM AUTHOR]

Abstract Determining the stereochemistry at the anomeric position of glycosides is imperative in chemical synthesis. As for 1,2- cis -β-glycosides such as β-mannosides, 13C-1H coupling constants, 1 J CH s, are conventionally used when glycosides are in an ordinary chair conformation. In this work, we searched for appropriate criteria to determine the stereochemistry of products in a recently developed glycosylation reaction using 2,6-lactones. As a result, we found that α-glycosides exhibited vicinal coupling constants of around 3.0 Hz at the anomeric proton, as well as a long-range coupling between protons at C-1 and C-5, whereas β-glycosides had coupling constants of 1.2 Hz at most. These figures are expected to be useful for future assignments. In addition, the observations obtained from this study revealed the conformation of glycosides with a 2,6-lactone moiety. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Glucose is the most abundant carbohydrate found in living organisms. It exists as two anomers: α-D-glucose and β-D-glucose, which differ in how the hydroxyl group on the C1 carbon is directed. In solutions, the ratio between α- and β-D-glucose is typically 4:6 but can vary depending on the surrounding ions or temperature. In this study, we obtained near-infrared (NIR) spectra of the glucose anomers based on concentration, and analyzed the spectral difference between each anomer by spectra subtraction and principal component analysis, respectively. Moreover, by simultaneously measuring the optical rotation and NIR spectra from dissolution to equilibration, we showed that NIR spectra quantitatively estimated the specific rotations of glucose solutions using partial least-squares regression in the 1100–1800 nm wavelength range. All the analytical results indicated that the absorption at 1742 nm possess the potential to distinguish each glucose anomer quantitatively. Therefore, we addressed the prediction of the specific rotation by the absorption at 1742 nm, and demonstrated that the absorption normalized by line subtraction showed the high correlation with measured specific rotation. The absorption at 1742 nm reflects structural changes of the glucose anomers in solution. Our spectroscopy study not only provides spectral information about glucose anomers, which are the most fundamental chemical compounds in organisms, but also shows the possibility to detect the anomer ratio in vivo for the fields of agriculture and medicine by taking advantage of NIR. [ABSTRACT FROM AUTHOR]

Abstract: Reported is the stereospecific cross‐coupling of anomeric stannanes with symmetrical diselenides, resulting in the synthesis of selenoglycosides with exclusive anomeric control. The reaction proceeds without the need for directing groups and is compatible with free hydroxy groups as demonstrated in the preparation of glycoconjugates derived from mono‐, di‐, and trisaccharides and peptides (35 examples). Given its generality and broad substrate scope, the glycosyl cross‐coupling method presented herein can find use in the synthesis of selenium‐containing glycomimetics and glycoconjugates. [ABSTRACT FROM AUTHOR]

Abstract: We report a Raman spectroscopy study of glucose, fructose, and mannose. The spectra have been recorded for the dry powders and for solutions in H2O and D2O and commented in the so‐called “fingerprint region” of the spectra (200–1,400 cm−1), in order to study the influence of the interaction with water on the solute vibrational modes. We have evidenced splitting of some bands, due to the presence of different anomers in solution. The isotopic substitution of the solvent has allowed in some instances to confirm the band assignment and, in other cases, to propose new assignments. Importantly, the isotopic substitution of the solvent has evidenced differences in the interaction of the investigated monosaccharides with water, which are rationalized as due to a balance between the inertia of the oscillator due to H‐bonding and bond strength. In particular, glucose and fructose interact strongly with water, whereas in the case of mannose, we have observed a weaker interaction with water and a different behaviour of its anomers. [ABSTRACT FROM AUTHOR]

Two cyclic diastereoisomeric structures, known as α- and β-anomers of d -glucose with different configurations around C1 with OH groups in axial or equitroial positions, undergo the mutarotation conversion to each other in water. Two-dimensional correlation and codistribution spectroscopy (2DCOS and 2DCDS) analyses were applied to the time-dependent ATR IR spectra of aqueous solutions of α- and β- d -glucose undergoing such mutarotation conversion. 2DCOS analysis reveals that the increase and decrease in the IR intensities after the dissolution of α- or β- d -glucose are not fully synchronized, suggesting the mutarotation of d -glucose in water is not a simple binary conversion process but a multi-step reaction involving an intermediate species with a finite and observable concentration level and lifetime. 2DCDS analysis of the time-dependent ATR IR spectra clearly demonstrated the presence of intermediate species contributing to the band positions overlapped close to bands for α- and β- d -glucose. The fact that band positions identified for the intermediate species for α- to β- d -glucose conversion are the same for the reverse reaction suggests that they arise from the same species, most likely the open-ring structure produced by the hydrolysis. [ABSTRACT FROM AUTHOR]

As counter parts of ILs, DESs have received general interest because of their comparable physicochemical properties to ILs and facile preparation from readily available chemicals. In this work, the isomeric distributions of fructose, glucose, xylose and GlcNAc in CCU, CCG and CCO, i.e. basic, neutral and acidic DES, have been determined by 13 C NMR. Higher furanose fraction of fructose was observed in CCO compared to CCG and CCU. The glucose was chosen as model compound to reveal the effect of DES on the mutarotation behavior with DMSO‑ d 6 as co-solvents. The experimental results showed that a high ratio of CCU to glucose speed up the mutarotation rate of glucose in DMSO‑ d 6 , but have little influence on the anomeric distribution. Furthermore, the mutarotation of glucose in DESs is mainly driven by the HBD, whereas HBA provides little influence. However, HBD and HBA display a synergistic effect on the glucose mutarotation process. Hydrogen bonding between hydrogen of amino in urea and oxygen of hydroxyl in glucose is the driving force for the interconversion of anomers. [ABSTRACT FROM AUTHOR]

Conformation of monosaccharides, including the ring shape, has for years been the subject of intensive research. Although d -aldohexopyranoses are the most extensively studied pyranoses, there also exist other groups of saccharides that contain analogous chemical system of the six-membered ring. Here we describe in details the results of the molecular dynamics-based conformational analysis concerning a series of pyranoses, namely: d -aldopentoses, d -ketohexoses as well as deoxy- ( d -quinovose, l -fucose, l -rhamnose) and dideoxy- (abequose, paratose, tyvelose, digitoxose) derivatives of aldohexoses. By using the carbohydrate-dedicated GROMOS 56a6 CARBO force field, we determined the conformational properties of both the lactol and hydroxymethyl groups as well as the anomeric populations for all considered compounds. The orientation of the lactol group follows the trend expected on the basis of the exo -anomeric effect for all compounds whereas the conformation of the hydroxymethyl group in d -ketohexoses is represented by the two gauche (with respect to the ring oxygen atom) rotamers. The special emphasis is put on the ring-inversion properties studied in the context of both the full chair-chair inversion and the chair-boat/skew-boat rearrangement. The calculated ring-distortion energies, compared with those obtained for regular d -aldohexopyranoses allowed for estimating the influence of particular substituents on the ring flexibility. Overall, such influence is correlated with the dimension of the substituent and its orientation but is limited to the case of the chair-chair inversion whereas the chair-to-boat/skew-boat rearrangement exhibits roughly the same properties for all pyranoses. For all d -aldopyranoses the α anomers exhibit lower ring-inversion free energies in comparison to the β anomers whereas this trend is inverted in the case of d -ketohexopyranoses. [ABSTRACT FROM AUTHOR]

The regioselective protection of both methyl galactopyranoside anomers at the 2 and 3-positions as the butane diacetal (BDA) is well known. Here we describe the formation of an unexpected byproduct, which mainly occurs when α-methyl galactopyranoside is reacted with 2,3-butanedione under BF 3 •OEt 2 catalysis. The structure of the byproduct, which did not arise from anomerisation to the β-anomer or from BDA formation at the galactopyranoside 3,4-positions, was elucidated by NMR and X-ray crystallographic analysis, and proved to be the expected BDA protected galactopyranoside, but in which the stereochemistry of both its BDA acetal centres are inverted. Interestingly, the conformation of the resulting six-membered BDA ring was distorted to a skew boat conformation in order to maintain anomeric stabilisation. [ABSTRACT FROM AUTHOR]

Energy-resolved collision-induced dissociation (ER-CID) experiments of sodium cationized glycosyl phosphate complexes, [GP+Na], are performed to elucidate the effects of linkage stereochemistry (α versus β), the geometry of the leaving groups (1,2- cis versus 1,2- trans), and protecting groups (cyclic versus non-cyclic) on the stability of the glycosyl phosphate linkage via survival yield analyses. A four parameter logistic dynamic fitting model is used to determine CID values, which correspond to the level of rf excitation required to produce 50% dissociation of the precursor ion complexes. Present results suggest that dissociation of 1,2- trans [GP+Na] occurs via a McLafferty-type rearrangement that is facilitated by a syn orientation of the leaving groups, whereas dissociation of 1,2- cis [GP+Na] is more energetic as it involves the formation of an oxocarbenium ion intermediate. Thus, the C1−C2 configuration plays a major role in determining the stability/reactivity of glycosyl phosphate stereoisomers. For 1,2- cis anomers, the cyclic protecting groups at the C4 and C6 positions stabilize the glycosidic bond, whereas for 1,2- trans anomers, the cyclic protecting groups at the C4 and C6 positions tend to activate the glycosidic bond. The C3 O-benzyl (3 BnO) substituent is key to determining whether the sugar or phosphate moiety retains the sodium cation upon CID. For 1,2- cis anomers, the 3 BnO substituent weakens the glycosidic bond, whereas for 1,2- trans anomers, the 3 BnO substituent stabilizes the glycosidic bond. The C2 O-benzyl substituent does not significantly impact the glycosidic bond stability regardless of its orientation. [ABSTRACT FROM AUTHOR]

Nitrogen mustards (NMs) are DNA-alkylating compounds that represent the earliest anticancer drugs. However, clinical use of NMs is limited because of their own mutagenic properties. The mechanisms of NM-induced mutagenesis remain unclear. The major product of DNA alkylation by NMs is a cationic NM-N7-dG adduct that can yield the imidazole ringfragmented lesion, N5-NM-substituted formamidopyrimidine (NM-Fapy-dG). Characterization of this adduct is complicated because it adopts different conformations, including both a canonical β- and an unnatural α-anomeric configuration. Although formation of NM-Fapy-dG in cellular DNA has been demonstrated, its potential role in NM-induced mutagenesis is unknown. Here, we created site-specifically modified singlestranded vectors for replication in primate (COS7) or Escherichia coli cells. In COS7 cells, NM-Fapy-dG caused targeted mutations, predominantly G → T transversions, with overall frequencies of ~11-12%. These frequencies were ~2-fold higher than that induced by 8-oxo-dG adduct. Replication in E. coli was essentially error-free. Toelucidate themechanismsof bypass of NM-Fapy-dG, we performed replication assays in vitro with a high-fidelity DNA polymerase, Saccharomyces cerevisiae polymerase (pol) δ. It was found that pol δ could catalyze high-fidelity synthesis past NMFapy- dG, but only on a template subpopulation, presumably containing theβ-anomeric adduct. Consistent with the low mutagenic potential of the β-anomer in vitro, the mutation frequency was significantly reduced when conditions for vector preparation were modified to favor this configuration. Collectively, these data implicate theα-anomeras amajorcontributor toNM-Fapy-dG-induced mutagenesis in primate cells. [ABSTRACT FROM AUTHOR]